The battery has become a primary power source for many portable electronic devices such as radios, hearing aids, watches, calculators, and the like. In order to maintain the overall electronic devices as compact as possible, the electronic devices are usually designed with cavities to accommodate miniature batteries as their source of power. The cavities are usually made so that a battery can be snugly positioned therein thus making electronic contact with appropriate terminals within the device. A major potential problem in the use of battery powered devices of this nature is that if the battery bulges, it usually becomes wedged within the cavity of the device which sometimes can result in damage to the device. One cause of cell bulging or other distortion of the cell's overall physical dimensions is due to the expansion of the cathode during discharge or during abusive discharge conditions. For example, in nonaqueous lithium/solid cathode systems, the cathode may expand and move into the anode compartment of the cell during discharge. Especially with improperly balanced cell components or under abusive cell conditions, it is common for this cathode expansion to cause cell distortion (bulging) which, in turn, may cause damage to the electronic device in which the cell is used. Since this type of cell distortion is due to the physical expansion of the cathode, then a possible solution to minimize any overall cell distortion is to provide a void or cavity within the cell to accommodate the expansion of the cathode. Within electronic technology geared to miniaturization, it becomes necessary to package the power supply in a miniature type package so that the device it is to power can be reduced in size. Consequently, providing cavities within the cell system to accommodate any electrode expansion is not economically feasible.
It is, therefore, an important object of this invention to provide a compact cell structure that can halt the expansion of the positive electrode of the cell during discharge so as to effectively eliminate distortion of the cell's housing.
Another object of the present invention is to provide a means whereby after the positive electrode of a cell expands to a predetermined amount, the cell is adapted for providing an internal short thereby effectively preventing the distortion of the housing of the cell.
Another object of the present invention is to provide a nonaqueous lithium/solid cathode cell system having means for internally shorting the cell after the positive electrode has expanded a predetermined amount.
Another object of the present invention is to provide a conductive member within a cell which is disposed so as to internally short the cell when the positive electrode expands a predetermined amount.
Another object of the present invention is to provide a pronged current collector disposed within the cell so that upon expansion of the positive electrode to a predetermined amount and partial consumption of the negative electrode, the positive electrode will contact the pronged current collector, will pierce the separator and contact the positive electrode, thereby internally shorting the cell.
The foregoing and additional objects will become more fully apparent from the following description and the accompanying drawings.